To date, most research on eating disorders has focused on girls and women. However, with youth overweight and obesity rates reaching epidemic proportions, pressure to be thin and lean has likely contributed to an increased risk for all youth to engage in disordered dieting and exercise behaviors. Such behaviors not only increase the risk for developing eating disorders, but may also contribute to future weight gain and the development of comorbid psychopathology (e.g., depression). Inadequate focus, however, has been devoted to the experiences of men and of sexual minorities (gay/lesbian, bisexual), in spite of emerging evidence that their body image socialization processes may differ from those of heterosexual women, and that gender expression and sexual orientation may impact cognitive and behavioral reactions to negative body image. Such findings necessitate future studies focused on the processes that underlie gender and sexual orientation differences in disturbed dieting and exercise. To address these research imperatives, the program of research will focus on the following aims: (1) Utilize multi-wave longitudinal data on physical development, body image socialization, and dieting and exercise behaviors to elucidate the development of heterosexual and sexual minority boys and girls' body image socialization and disordered dieting and exercise behaviors. Analyses will examine the diversity in pathways to disordered dieting and exercise, and investigate how gender, sexual orientation, and the interactions between the two are linked to such developmental variability. (2) Elucidate factors that contribute to the development of boys' negative body image socialization and disordered dieting and exercise behaviors. In particular, the research will focus on pubertal development, gender expression (i.e., gender conformity), and the development of the muscularity ideal. (3) Identify unique and shared longitudinal predictors of eating disorder risk among the sexual minority subgroups, paying particular attention to gender, gender expression, level of identity disclosure (i.e., outness), identity-related distress, and sexual minority community involvement. Findings will help clarify how sexual orientation serves as both a risk and protective factor for disordered dieting and exercise behaviors. To fulfill these aims the research will utilize national data from the Growing Up Today Study, a nine-wave longitudinal cohort study begun in 1996 of over 16,000 youth who were recruited when they were between the ages of 9-14 and who are now in their mid 20s. A combination of longitudinal statistical methods (e.g., growth mixture modeling) will be used to examine diversity in the development of disordered dieting and exercise. The proposed research will be among the first to examine the confluence of physical development, body image socialization, and the emergence of disordered dieting and exercise among males and females of all sexual orientations. Findings will clarify key mechanisms of health risk and promotion as well as inform interventions. PUBLIC HEALTH RELEVANCE: Eating disorders represent a tremendous cost to society, affecting productivity, physical health, social relationships, and well being. New research regarding gender and sexual orientation differences in the manifestation and prevalence of disturbed dieting and exercise suggest that boys and sexual minorities are understudied and underserved populations. Studying the unique risk and protective factors that create differential risk for boys and sexual minority subgroups has the potential to inform dieting and exercise disorder interventions for all youth.